Who says you’re lonely just because you’re alone?

When “The Perks of Being a Wallflower” was published in 1999, some schools in the United States banned it from their libraries and reading lists for its depictions of graphic sexual scenes, drugs, homosexuality and teen pregnancy — the usual suspects. Of course, this only increased its street cred.

At the same time, in many U.S. bookstores it’s on display next to “The Catcher in the Rye,” a fact that makes author Stephen Chbosky extremely proud. “I’ve read ‘Catcher in the Rye’ so many times as a kid,” he tells The Japan Times. “A lot of people have said that this book is like the millennial version of ‘Catcher’ and they see Holden Caulfield in (the protagonist) Charlie.

“(But) I think these are two entirely different stories and Charlie and Holden are two different people with their own voices and unique perspectives. J.D. Salinger was a great influence on me, but then so were F. Scott Fitzgerald and Stephen King and Ernest Hemingway and countless others. I wasn’t trying to mimic anyone’s style, but I did want to stress and also portray the importance of loving great books.”

Chbosky describes Salinger’s book as “an American classic,” but he hesitates to categorize his own. “Some people touted it as Y.A. (young adult), but I don’t know,” he says. “I guess that part is still a mystery. I just loved writing it, and loved developing the characters; especially Charlie, who isn’t exactly me, but there’s a lot of myself in him.”

And now “Perks” has become a movie, adapted by Chbosky himself and with Logan Lerman as Charlie and Emma Watson as the lovely and sensitive Sam.

“I never sold the rights, I never optioned it. I always knew I would direct the movie myself,” says Chbosky; this is actually his second shot at directing. “It was my dream, and I just needed the time and distance to actually do it.”

The critical success of his film overseas has brought in a deluge of project offers. His next film is “While We’re Young,” which marks a second team-up with Watson.

“I love working with Emma,” says Chbosky. “I love working with actors in general, but working on set with the team that I had (for this movie) was just freaking wonderful. What I loved was seeing Emma and Ezra Miller and Logan Lerman be high school kids, because I realized that none of them had ever had a normal school experience. They all grew up on movie sets. So prom and parties — this stuff was new to them.”

“Perks” is a celebration of “misfit toys,” as Sam describes herself, her half-brother Patrick (Miller) and Charlie. The story is set in the early 1990s, when outsiders like them had no nifty tools like social networking to hook them up with society and keep them from loneliness. Such kids were on their own, and “Perks” hums with their restrained but ready energy and roots for their struggle to live out youth on their own terms.

Such introverts have suddenly become cool, if not exactly mainstream; writer and lecturer Susan Cain extolled the “power of introverts” on what quickly became a classic TED talk in 2012. Did Chbosky think that his movie could have had an influence on the introvert boom as well?

“Introverts may be shy, but they’re not antisocial,” he says. “They’re just not party people, though this could be a stigma for any young person battling feelings of insecurity. Because, you know, in the U.S. not being a party animal in high school can be rough. That goes for adults too, as the culture puts a lot of value on getting to know people and being popular.

“Americans also set store on friendliness, and when you’re a wallflower at a social gathering, people can misinterpret that in a bad way. But that’s not it at all. It could just mean you’re not ready to talk or mix just yet, and you like to be quiet. There’s nothing wrong with that. I think the fact that (American) people have come to accept introverts is because they recognize that such behavior is OK, or even cool.”

The now widely acknowledged definition of an introvert is someone who is, among other things, uncomfortable with small and/or loud talk, who has no trouble being alone and who tends to think before speaking. In the movie of “Perks,” Charlie has all these traits, and until he meets Sam and Patrick, he’s inwardly plagued by them. When the pair come up to him at a party to say hello, he’s genuinely surprised. “I didn’t think anyone noticed me,” says Charlie.

“That’s the refrain of the high school misfit, isn’t it?” says Chbosky. “They often go around thinking they’re invisible. And that could be the cause of a lot of pain.”

In the end, says Chbosky, he wanted people to come away from the book and the movie feeling happier than they did before.

“I once got a letter from a reader saying she had never felt loved before reading the book,” he says. “That just blew me away. ‘The Perks’ — both the book and the movie — are about the how you are not alone. What you’re going through is valid; you deserve respect and to be loved. If people are feeling down, I want them to have a sense of hope through watching the film.”